3rd generation (3G) systems, such as the Universal Mobile Telecommunication System (UMTS) have been developed and deployed to further enhance the communication services provided to mobile users compared to those communication services provided by the 2nd generation (2G) communication system known as the Global System for Mobile communication (GSM).
As is well known, cellular communication systems, such UMTS, provide communication to mobile devices via a plurality of cells, with each cell served by one or more base stations. The base stations are interconnected by a fixed network which can communicate data between the base stations. A mobile device communicates via a radio communication link with a base station of the cell within which the mobile station is situated. In UMTS, the base stations which are part of the UTRAN are known as Node Bs and a mobile device is known as User Equipment (UE).
In order to extend coverage and capacity indoors, such as in residential or commercial or small business environments and especially where access would otherwise be limited or unavailable, systems with smaller sized cells served by small base stations, known as femtocells, have been developed. The femtocell incorporates the functionality of a typical base station and some network functionality to allow a simpler, self contained implementation. Current femtocell designs can typically support two to four active mobile devices in a residential setting and thus, are typically used for a closed subscriber group (CSG) or private cell where only subscribers in the group may communicate via the femtocell (also known as private base station). Different architectures for femtocells have been proposed. For example, a UMTS femtocell architecture contains a Home Node B (HNB), and a 3G HNB Gateway (3G HNB GW), which interfaces with the UMTS Packet Switched (PS) and Circuit Switched (CS) domains. The third Generation Partnership Project (3GPP) refers to a 3G femtocell that connects a 3GPP UE to a core network over UTRAN as a Home Node B (HNB) and is working currently to complete a new HNB standard for Rel-8 of specifications: see for example, the 3GPP document TS 25.467 (UTRAN Architecture for 3G HNB).
3GPP has defined an architecture to support access to the PS domain and to the CS domain of one or more core networks through HNBs. FIG. 1 is a simplified diagram showing one HNB 10 serving a private cell 12, and a Node B (NB) 14 serving a larger cell 16 (referred to as a macro cell). UE 13 communicates with the HNB 10 over a radio communication link 15 and the HNB 10 communicates with a 3G HNB gateway 18 via a Iuh interface 20. NB 14 is coupled to Radio Network Controller (RNC) 22 as is well known in the art. Services are provided to the UE 13 via the CS domain 23 using the lu-cs interface and the Mobile Switching Centre (MSC) 24. IP services are provided to the UE 13 via the PS domain 25 using the lu-ps interface and the Serving GPRS Support Node (SGSN) 26 and the Gateway GPRS Support Nodes (GGSN) or Packet Data Network Gateway (PGW) 28. For UEs having IP Multimedia Subsystem (IMS) capability, access to IMS services may be provided using IMS elements of the IMS 27, the lu-ps interface and the SGSN 26 and the GGSN/PGW 28.
In addition, 3GPP is working to specify an enhanced HNB architecture in the context of Rel-9: see for example, the 3GPP document TS 22.220, the disclosure of which is incorporated herein by reference.
In the enhanced HNB architecture, access to 3G and evolved 3G (EPS) services may be provided by a Public Land Mobile Network (PLMN) by means of HNBs and Home evolved Node Bs (HeNBs) which are jointly referred to as H(e)NB. A HeNB is a 3G femtocell that connects a 3GPP UE over an Evolved UTRAN (EUTRAN) wireless air interface to a core network using, for example, a broadband IP backhaul, such as the internet connections available in homes through cable or Digital Subscriber Lines (DSL).
In a PLMN communication system, there may be a number of CSG cells and all the H(e)NBs (and hence the CSG cells) serving the same CSG share the same unique (within the PLMN) identity called the CSG Identity. TS 22.220, Section 5.5.4, states that the UE shall contain a network (e.g. operator) controlled list of allowed CSG Identities (referred to as the Allowed CSG list) which list identifies those CSG cells to which the UE is allowed access. In addition, TS 22.220 states that the UE shall contain a user controlled list of allowed CSG Identities (referred to as the User CSG list) which list identifies the allowed CSG cells which have been selected by the user. For example, the user controlled list may include the user's home CSG cell or the user's most frequently used CSG cells.
As the UE moves into and out of CSG cells and between neighbouring CSG cells when in idle mode (i.e. when the UE is active with (that is, registered to) the PLMN but no communication resources have been allocated to the UE) or on turn on of the UE, it may be necessary to select a ‘new’0 CSG cell for communication and to register the UE on a PLMN via the H(e)NB serving the ‘new’ CSG cell. CSG cell (re)selection may be performed by standard automatic network selection procedures which typically use the radio signal strength to select a suitable ‘new’ CSG cell, which is preferably a CSG cell whose CSG Identity is in the Allowed CSG list or the User CSG list.
Using normal cellular cell reselection criteria with consideration of radio signal strength works well for reselection of macro cells in current cellular systems because the macro cells of the cellular systems are well planned and optimised. Using radio signal strength only as a reselection criteria also works well with WLAN with manual selection because as long as the radio signal strength is above a threshold, the UE will stick to the WLAN. For CSG cell selection, due to the fact that the coverage of the CSG cells is typically not well planned from a radio perspective compared to macro cells of a cellular system, selecting a ‘new’ CSG cell based on radio signal strength may not result in the preferred CSG cell of a user being selected.
For example, in a block of flats there may be several CSG cells with overlapping coverage and with transmitters transmitting at different powers, and the home CSG cell may not provide the strongest radio signal in all rooms of the user's home flat. Thus, by selecting a CSG cell based on radio signal strength, the UE, even when the user is at home, may end up being registered to a neighbour's CSG cell rather than the preferred home CSG cell. The home CSG cell is typically the preferred CSG cell due to lower billing rates and the fact that the user can use the local services provided via the home CSG cell (e.g. local printer on home network). Thus, with current reselection criteria based on radio signal strength, a UE when at the user's home may select a neighbours CSG cell at a higher billing rate.
Selection of a CSG cell may also be performed manually by a user. In this case, the user can request the UE to perform a scan for available CSG Identities. When such a request is received the UE performs a scan for available CSG cells, and their CSG Identities. Following the scan, the CSG Identities of the available CSG cells are displayed on the UE display. An indication is given to the user as to which of the available CSG Identities is contained in the Allowed CSG list or the User CSG list. TS 22.220, Section 5.5.4, specifies that the available CSG Identities shall be displayed in the following order:                The CSG Identities that are contained in the User CSG list.        The CSG Identities that are contained in the Allowed CSG List.        Any other CSG Identity not included in the Allowed CSG List or User CSG list.        
The user may then select an entry in the list, and in response to the selection, the UE may reselect any of the available CSG cells with the CSG Identity chosen by the user and attempt to establish communication with that CSG cell.
Since the user may be presented with several lists of CSG Identities, the display of lists in this way in order to enable a user to select a CSG cell is not particularly user friendly.
In addition, since the billing rates or subscription offerings may vary significantly between different CSG cells of the CSG Identities, even between CSG Identities in the same list, even prioritising between the different lists (e.g. the User CSG list and the Allowed CSG list) does not enable the preferred CSG Identity for a user to be easily determined.
For example, in the case of an airport location having a CSG owned by an airline and CSG owned by a restaurant, the CSG Identities of both these CSGs may be included in the User CSG list through manual selection. As there is often a revenue sharing agreement between the CSG owner and network operator, a CSG owner may want to motivate more uses of their HeNB by having some rebate/reward point program. For example, the airline may advertise the more a user uses their CSG, the more frequent flier miles the user can earn. So in this case a user may prefer to use the airline CSG over the restaurant CSG. However, as discussed above, the user is merely presented with a list of the CSG Identities in the User CSG list which does not make it easy to select a preferred CSG.